Projection exposure apparatuses for semiconductor lithography serve to expose structures onto a substrate coated with photosensitive materials. Typically, the substrate is predominantly composed of silicon and is referred to as a wafer. The wafer can be used to produce semiconductor components, such as, for example, computer chips.
FIG. 1 illustrates an exemplary projection exposure apparatus 1 according to the prior art. The projection exposure apparatus 1 includes an illumination device 3, a device 4 for receiving and exactly positioning a mask provided with a structure, a so-called reticle 5, which determines the later structures on a wafer 2. The projection exposure apparatus also includes a device 6 for holding, moving and exactly positioning precisely the wafer 2, and an imaging device 7, commonly referred to as a projection objective 7. The device 7 has a plurality of optical elements 8 mounted via mounts 9 in an objective housing 10. Exemplary optical elements include lenses, mirrors, prisms, terminating plates and the like.
The illumination device 3 provides a projection beam 11 to image the reticle 5 on the wafer 2. The projection beam 11 can be, for example, light or more generally generally electromagnetic radiation. A laser or the like can be used as a source of the radiation. The radiation is shaped via optical elements in the illumination device 3 such that the projection beam 11 has the desired properties with regard to diameter, polarization, shape of the wavefront and the like when it impinges on the reticle 5. An image of the reticle 5 is generated via the projection beam 11 and is correspondingly transferred to the wafer 2 by the projection objective 7.
With this arrangement, the projection exposure apparatus 1 allows structures in the reticle 5 to be imaged onto the wafer 2. After being exposed to the projection beam 11, the wafer 2 can be moved in the direction of the arrow, so that a multiplicity of individual fields of the wafer 2 (areas of the wafer 2) can be exposed. In some instances, the reticle 5 is scanned continuously through a slotted diaphragm.